Treatment system for synergistically enhancing antibiotic removal by plants and modified canna biochar

Abstract

The invention provides a treatment system for synergistically enhancing antibiotic removal by plants and modified canna biochar, which comprises a sequencing batch reactor, the sequencing batch reactor is provided with a water inlet, a water outlet, an aeration mechanism and a stirring mechanism, the bottom of the sequencing batch reactor is provided with an activated sludge coupling modified canna biochar zone, and the activated sludge coupling modified canna biochar zone is provided with a water outlet. A canna plant area is arranged at the upper part of the sequencing batch reactor, and canna is planted in the canna plant area; the water inlet is positioned at the lower part of the sequencing batch reactor, the water outlet is positioned at the upper part of the sequencing batch reactor, and the aeration mechanism and the stirring mechanism are positioned in the activated sludge coupling modified canna biochar area; the modified canna biochar is obtained by performing high-temperature cracking on canna residues and then treating the canna residues with a strong acid or strong alkali solution. By adopting the technical scheme of the invention, the removal rate of antibiotics is greatly improved, the emission of greenhouse gases is reduced, and the method is green and environment-friendly.

Description

Technical Field

[0001] The invention relates to the technical field of sewage treatment and environmental protection, and in particular to a treatment system for synergistically enhancing antibiotic removal by using plants and modified canna biochar. Background Art

[0002] In recent years, with the widespread use of antibiotics in medicine, animal husbandry and agriculture, their residues entering the water environment have become an increasingly serious problem. Antibiotics enter natural water bodies through human and animal excrement and eventually flow into sewage treatment systems. A large number of studies have shown that even at low concentrations, antibiotics may still pose potential hazards to microbial communities, ecosystems and human health in the environment, including the spread of antibiotic resistance genes and the spread of resistant pathogens. At the same time, the presence of antibiotics in sewage treatment may aggravate greenhouse gas emissions, especially under anaerobic conditions, which will promote the production of greenhouse gases such as methane. Therefore, the effective removal of antibiotics is not only an important research direction in the current sewage treatment field, but also one of the key measures to reduce greenhouse gas emissions. By optimizing the sewage treatment system and avoiding the inhibition of microbial metabolism by antibiotics, it is helpful to reduce the production of greenhouse gases and achieve more environmentally friendly sewage treatment.

[0003] The activated sludge method is currently the most commonly used biological treatment method in municipal sewage treatment plants, which removes organic pollutants from sewage through microbial metabolism. However, conventional activated sludge systems face great challenges in removing antibiotics. For example, the molecular structure of antibiotics is complex, and they have strong chemical stability and antimicrobial properties, which makes it difficult for ordinary microorganisms in sludge to effectively degrade antibiotics, resulting in poor removal effects. In addition, antibiotics themselves have antibacterial and bactericidal effects. After entering the activated sludge system, they will inhibit the normal metabolic activity of microorganisms, especially affecting the growth of some sensitive strains. This not only reduces the overall treatment efficiency of activated sludge, but may also cause disorder of the microbial community in the sewage treatment system. In addition, antibiotics may be partially adsorbed on the sludge surface or microbial cell wall in the activated sludge system, but this adsorption is temporary. The adsorbed antibiotics are prone to desorption under certain conditions and re-enter the water body, resulting in unstable removal of antibiotics by the system. Therefore, it is difficult to completely remove antibiotics from sewage by relying solely on the activated sludge method. Finally, after antibiotics enter the activated sludge system, they will inhibit the normal metabolic activity of microorganisms, especially having a negative impact on the growth of sensitive strains. This inhibition not only reduces the removal efficiency of antibiotics in the activated sludge system, but also may cause the microorganisms to be unable to effectively carry out aerobic metabolism, making the system more likely to enter an anaerobic state. Under anaerobic conditions, microorganisms metabolize pollutants and produce a large amount of greenhouse gases such as methane and nitrous oxide, which increases greenhouse gas emissions during sewage treatment. Summary of the invention

[0004] In view of the above technical problems, the present invention discloses a treatment system for synergistically enhancing antibiotic removal by plants and modified canna biochar. By coupling the adsorption of modified canna biochar in the rhizosphere of plants and the biodegradation of activated sludge, efficient removal of antibiotics is achieved, overcoming the problems of limited antibiotic treatment capacity and large greenhouse gas emissions of conventional activated sludge systems and plant adsorption methods.

[0005] To this end, the technical solution adopted by the present invention is:

[0006] A treatment system for synergistically enhancing antibiotic removal by plants and modified canna biochar comprises a sequencing batch reactor. The sequencing batch reactor is provided with a water inlet, a drain outlet, an aeration mechanism and a stirring mechanism.

[0007] The bottom of the sequencing batch reactor is provided with an activated sludge coupled modified canna biochar zone, the upper part of the sequencing batch reactor is provided with a canna plant zone, and the canna plant zone is planted with canna; the water inlet is located at the lower part of the sequencing batch reactor, the drain outlet is located at the upper part of the sequencing batch reactor, and the aeration mechanism and the stirring mechanism are located in the activated sludge coupled modified canna biochar zone;

[0008] The modified canna biochar is obtained by subjecting canna residue to high-temperature pyrolysis and then treating it with a strong acid or strong alkali solution.

[0009] With this technical solution, the canna plant area is set in the upper area of ​​the sequencing batch reactor, and aquatic plants such as canna are planted. This plant area is coupled with the modified canna biochar and activated sludge system through the adsorption and metabolic functions of the plant roots, and synergistically removes antibiotics from sewage. The canna plant has a well-developed root system and a large adsorption surface area, which can capture antibiotic molecules in sewage through physical adsorption. At the same time, the canna root system also transforms or degrades some of the adsorbed antibiotics through metabolism, thereby reducing the concentration of antibiotics. Substances such as organic acids and enzymes in plant root secretions can promote the degradation reaction of antibiotics and improve the ability of plants to remove antibiotics.

[0010] In addition, the developed root system of Canna can not only adsorb antibiotics, but also a large amount of activated sludge. The porous structure of the root surface and the polysaccharides secreted by it can provide a place for the microbial community in the activated sludge to attach, forming a stable microbial ecosystem. The attachment of activated sludge enhances the biodegradation capacity of the plant rhizosphere, and further degrades antibiotics and other organic pollutants adsorbed in the rhizosphere through the metabolic activities of microorganisms. Through this root-activated sludge coupling, microorganisms and plant roots work synergistically to form a highly active microecological environment in the rhizosphere, promoting the degradation of antibiotics. The microorganisms in the activated sludge not only use the nutrients secreted by the roots to maintain their own metabolism, but also can efficiently degrade the antibiotic molecules adsorbed on the roots. This synergistic effect greatly improves the overall antibiotic removal efficiency of the system.

[0011] The large amount of activated sludge and modified canna biochar adsorbed by plant roots together provide an ideal habitat for microorganisms in the rhizosphere. Microorganisms degrade antibiotic molecules adsorbed on modified canna biochar and root surfaces through metabolic activities. The efficient adsorption characteristics of modified canna biochar combined with the degradation function of plant root microorganisms significantly improve the efficiency of antibiotic removal. The rhizosphere microbial community further reproduces with the support of plant root secretions and continuously degrades antibiotics through co-metabolism and enzymolysis. This system, which combines the action of activated sludge, modified canna biochar and microorganisms adsorbed by plant roots, not only effectively improves the removal rate of antibiotics, but also enhances the stability and sustainability of the sewage treatment process.

[0012] Modified Canna biochar is a porous carbon material prepared by high-temperature pyrolysis of biomass (such as plant residues or agricultural waste), with rich pore structure and good adsorption performance. However, unmodified raw biochar has problems such as limited adsorption capacity and low selectivity when adsorbing complex organic pollutants (such as antibiotics). The technical solution of the present invention uses an acid-base modification method to treat Canna biochar, change the surface chemical properties of biochar, increase its specific surface area and pore volume, enhance its adsorption capacity for antibiotics, and provide a good attachment environment for microorganisms. Among them, acid modification mainly exposes more active sites by removing ash and inorganic substances on the surface; while alkali modification increases surface functional groups, especially oxygen-containing functional groups, thereby improving the affinity and binding ability for antibiotic molecules. In the pores of modified Canna biochar, antibiotics are adsorbed and fixed in large quantities, reducing their diffusion in water bodies. In addition, the surface functional groups of modified Canna biochar can be combined with antibiotic molecules through mechanisms such as physical adsorption, electrostatic action and chemical adsorption, further enhancing the removal effect of antibiotics.

[0013] The Canna plant area is one of the core components of this system. It is located in the upper area of ​​the reactor and combines the degradation function of activated sludge and microorganisms in the plant root system with the strong adsorption capacity of modified Canna biochar. This area forms an efficient antibiotic removal system by coupling activated sludge and modified Canna biochar to adsorb on the plant root system, which can achieve the dual effects of adsorption and degradation of antibiotics. During the stirring process, antibiotics in the sewage are adsorbed in large quantities by Canna biochar. At the same time, Canna biochar and activated sludge containing a large amount of antibiotics are adsorbed on the plant root system; during the static stage, the adsorbed antibiotics are removed by microorganisms at a high speed; and during the next stirring process, Canna biochar and activated sludge adsorbed on the plant root system are updated. In this technical solution, modified Canna biochar is used as the core adsorption material, and its efficient adsorption capacity significantly improves the removal effect of antibiotics. Specifically, the porous structure of modified Canna biochar can not only quickly adsorb antibiotics in water, but also provide a microenvironment for the attachment and survival of microorganisms in activated sludge and plant roots, promoting the degradation of microorganisms. The synergistic effect of the three further enhances the efficiency of antibiotic removal.

[0014] Microorganisms in activated sludge are secondary degraders in sewage treatment. In the activated sludge coupled modified canna biochar area, microorganisms not only degrade antibiotics through their own metabolic activities, but also use antibiotics attached to the surface of modified canna biochar to further improve the removal efficiency. Modified canna biochar provides a stable microbial attachment environment, promotes the reproduction and metabolism of microorganisms, and enhances the antibiotic degradation capacity in the sludge system. Activated sludge microorganisms gradually decompose antibiotic molecules into small molecules or even harmless substances such as water and carbon dioxide through co-metabolism, enzymatic reactions and other pathways. It can be seen that in the activated sludge and modified canna biochar coupling area, the adsorption effect of modified canna biochar and the degradation effect of activated sludge complement each other to form an efficient antibiotic removal system. Modified canna biochar reduces the toxic inhibitory effect of antibiotics on microorganisms through adsorption, enabling microorganisms to more effectively degrade antibiotics in sewage. In addition, over time, the antibiotics adsorbed on the surface of modified canna biochar are gradually degraded by microorganisms, and the adsorption sites of modified canna biochar are regenerated, maintaining the long-term treatment capacity of the system.

[0015] As a further improvement of the present invention, the modified Canna biochar is prepared by the following steps:

[0016] The collected canna is cut into segments, washed, dried, crushed, and placed in a tubular furnace, heated to 850-900°C in an oxygen-deficient state, kept warm for more than 1 hour, and ground after cooling to obtain canna biochar;

[0017] Concentrated nitric acid is added to the canna biochar, and the mixture is stirred for reaction for 2 hours, followed by filtering, washing, and drying to obtain modified canna biochar; or a KOH solution is added to the canna biochar, and the mixture is stirred for reaction at 60° C. to 80° C. for 2 hours, followed by filtering, washing, and drying to obtain modified canna biochar.

[0018] As a further improvement of the present invention, nitrogen is introduced into the tubular furnace, and the heating rate is 5-15° C. / min.

[0019] As a further improvement of the present invention, the concentration of the KOH solution is not less than 2 mol / L.

[0020] As a further improvement of the present invention, the area of ​​the canna plant zone is 20%-40% of the cross section of the sequencing batch reactor.

[0021] As a further improvement of the present invention, the activated sludge coupled modified canna biochar zone uses activated sludge and modified canna biochar mixed in a mass ratio of 1:8-12. Further, the activated sludge coupled modified canna biochar zone uses activated sludge and modified canna biochar mixed in a mass ratio of 1:10.

[0022] The present invention also discloses a sewage treatment method, which uses the above-mentioned plant and modified canna biochar synergistically enhanced antibiotic removal treatment system for treatment.

[0023] As a further improvement of the present invention, the sewage treatment method comprises the following steps:

[0024] Step S1, the sewage containing antibiotics enters the sequencing batch reactor through the water inlet;

[0025] Step S2, starting the stirring mechanism to stir for at least 250 minutes;

[0026] Step S3, stopping stirring and starting the aeration mechanism for aeration for at least 250 minutes;

[0027] Step S4, stopping aeration and allowing the mixture to settle for at least 100 minutes;

[0028] Step S5, after the upper layer of water after sedimentation becomes clear, draining the water through the drain outlet;

[0029] Repeat steps S1 to S5 to perform the next processing cycle.

[0030] With this technical solution, in the water inlet stage of step S1, sewage containing antibiotics enters the sequencing batch reactor through the water inlet and first flows through the canna plant area. The antibiotics in the sewage are adsorbed by the plant roots in this process and enter the modified canna biochar layer. The modified canna biochar adsorbs a large amount of antibiotics through its pore structure, fixes them on the surface and pores of the carbon, and prevents the antibiotics from flowing with the sewage. Steps S2 and S3 are aeration and degradation stages, and the stirring mechanism is used to evenly distribute the pollutants in the sewage to ensure that the antibiotics are fully in contact with the modified canna biochar, activated sludge and plant roots, thereby improving the removal efficiency of the antibiotics. In the aeration stage, the aeration mechanism is started to provide oxygen to the activated sludge area, promote the metabolic activity of microorganisms, and ensure the aerobic metabolism of microorganisms. At this time, the microorganisms further process the antibiotics in the sewage through degradation. At the same time, the antibiotics adsorbed by the modified canna biochar are gradually degraded by microorganisms, thereby reducing the concentration of antibiotics in the sewage. The stirring device is started at this stage to ensure that the antibiotics are in full contact with the plant roots, modified canna biochar and activated sludge, thereby improving the treatment efficiency of the antibiotics. Steps S4 and S5 are the sedimentation and drainage stages. After aeration and stirring, the system enters the sedimentation stage. The activated sludge and other suspended solids gradually settle to the bottom of the reactor, and the treated clean water accumulates in the upper layer. After multiple treatments of plant adsorption, modified canna biochar adsorption and activated sludge degradation, the antibiotic concentration in the sewage is significantly reduced to meet the discharge standards. Finally, the clean water is discharged from the system through the drain.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] The technical solution of the present invention adopts a coupling system of plants and modified canna biochar in synergy with activated sludge, combines the adsorption effect of plants, the strong adsorption effect of modified canna biochar and the microbial degradation effect of activated sludge, greatly improves the removal rate of antibiotics, and the removal rate of antibiotics in treated sewage can reach 70-80%. Among them, the removal rate of sulfamethoxazole can reach more than 90%, and the removal rate of ofloxacin can reach 70%-80%. After treatment, the concentration of antibiotics in sewage meets the national emission standards, the system runs stably, is easy to operate, and is suitable for large-scale sewage treatment plants.

[0033] Secondly, the modified canna biochar quickly adsorbs antibiotics during the reaction process, reducing the chance of antibiotics directly acting on microorganisms in activated sludge, reducing the toxic inhibitory effect of antibiotics on microorganisms, ensuring the microbial metabolic activity of the system, and improving the antibiotic removal capacity of the system; the system is forced to be maintained under aerobic conditions, the aerobic metabolism of microorganisms in the system is enhanced, and the amount of nitrous oxide generated is relatively reduced. In the experiment, 15.09 mg of nitrous oxide emissions can be reduced per cubic meter of sewage. This further shows that the present invention not only improves the pollutant removal efficiency by maintaining an aerobic environment, but also reduces the carbon footprint in the sewage treatment process. Moreover, canna plants and modified canna biochar are both natural materials, green and environmentally friendly, and do not produce secondary pollution.

[0034] Third, the use of two natural materials, canna plants and modified canna biochar, reduces the use of chemical agents, does not produce secondary pollution, and has green and environmentally friendly characteristics. In addition, the preparation cost of modified canna biochar is low, and the system operation cost is low, which is suitable for large-scale promotion and application. It is easy to operate and has strong adaptability, which is suitable for sewage treatment needs of different scales.

[0035] Fourth, the system of the present invention effectively reduces the generation of greenhouse gases and carbon emissions during sewage treatment by optimizing the microbial metabolic environment, improving the efficiency of antibiotic removal, and reducing the demand for energy, and has significant environmental advantages. In addition, the use of a sequencing batch reactor allows the system to have high operational flexibility when treating antibiotic sewage, and can flexibly adjust operating parameters according to treatment requirements. The system is easy to maintain and is suitable for sewage treatment facilities of various sizes. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a schematic structural diagram of a treatment system for synergistically enhancing antibiotic removal using plants and modified canna biochar according to an embodiment of the present invention.

[0037] Figure 2 It is an SEM image of the modified canna biochar of an embodiment of the present invention; wherein, a1~a4 are 500 times, 2000 times, 5000 times and 10000 times of unmodified canna biochar, b1~b4 are 500 times, 2000 times, 5000 times and 10000 times of acid-modified canna biochar HBC, c1~c4 are 500 times, 2000 times, 5000 times and 10000 times of alkali-modified canna biochar KBC.

[0038] Figure 3 3. It is the Fourier transform infrared spectra of the canna biochar before and after the adsorption of SMX and OFLX in the embodiment of the present invention; wherein, a) is the Fourier transform infrared spectra of BC, HBC and KBC before and after the adsorption of SMX, and b) is the Fourier transform infrared spectra of BC, HBC and KBC before and after the adsorption of OFLX.

[0039] Figure 4 3 is the adsorption kinetic curve of SMX by the canna biochar before and after modification according to the embodiment of the present invention; wherein a) is the curve of the adsorption amount changing with time, and b) is the curve of the adsorption amount changing with the square root of time under the intra-particle diffusion model.

[0040] Figure 5 3 is the adsorption kinetic curve of OFLX by the canna biochar before and after modification according to the embodiment of the present invention; wherein a) is the curve of the adsorption amount changing with time, and b) is the curve of the adsorption amount changing with the square root of time under the intra-particle diffusion model.

[0041] Figure 6 It is an analysis chart of the removal rate of SMX and OFLX by the treatment system according to an embodiment of the present invention.

[0042] The reference numerals include: 1-sequencing batch reactor, 2-canna, 3-water inlet, 4-drainage outlet, 5-stirring mechanism. DETAILED DESCRIPTION

[0043] The preferred embodiments of the present invention are described in further detail below.

[0044] like Figure 1 As shown, a treatment system for synergistically enhancing antibiotic removal by plants and modified canna biochar comprises a sequencing batch reactor 1, wherein the sequencing batch reactor 1 is provided with a water inlet 3, a drain outlet 4, an aeration mechanism and a stirring mechanism 5, wherein an activated sludge coupled modified canna biochar zone is provided at the bottom of the sequencing batch reactor 1, and a canna plant zone is provided at the top of the sequencing batch reactor 1, wherein canna 2 is planted in the canna plant zone; the water inlet 3 is located at the bottom of the sequencing batch reactor, the drain outlet 4 is located at the top of the sequencing batch reactor, the aeration mechanism and the stirring mechanism 5 are located at the activated sludge coupled modified canna biochar zone, and the stirring mechanism 5 comprises a stirring paddle. The modified canna biochar is obtained by high temperature cracking of canna residue and then treating it with a strong acid or strong alkali solution.

[0045] The sequencing batch reactor is the main treatment unit of this system, which has a water inlet, a drain, an aeration device and a stirring device. The size of the reactor can be designed according to the actual sewage treatment capacity, and is suitable for treating antibiotic-contaminated water bodies of different sizes such as municipal sewage, agricultural wastewater and industrial wastewater. In this embodiment, the reactor volume is 10L, the treated water is artificially prepared domestic sewage, and the concentration of the simulated antibiotic is 100ppb.

[0046] Furthermore, the canna plant area is located at the upper part of the reactor and is mainly used to grow aquatic plants such as canna. The area of ​​the plant area accounts for 20%-40% of the upper space of the entire reactor. The plants absorb antibiotics in the sewage through their developed root systems and promote the growth of microorganisms in the rhizosphere. Canna plants have the characteristics of tolerating antibiotic pollution in sewage and can partially absorb and metabolize antibiotics.

[0047] The modified canna biochar is set in the bottom area of ​​the system, usually mixed with activated sludge in different proportions, and attached to the plant roots during the stirring stage, with a thickness of 10 cm. Canna biochar is prepared from canna residue through a 900°C tubular furnace and then modified with an acid-base solution. The modified biochar has a rich pore structure and a large specific surface area, and can adsorb a large amount of antibiotics. The modified canna biochar not only plays a role in adsorbing antibiotics, but also provides a matrix for microorganisms to attach and grow.

[0048] The activated sludge area is located at the bottom of the sequencing batch reactor. This area is rich in various efficient microorganisms, which carry out metabolic activities under the action of the aeration device and can degrade antibiotics and other organic pollutants in sewage. The activated sludge concentration can be controlled at 5000mg / L. During the stirring process, the modified Canna biochar is adsorbed onto the rhizosphere activated sludge, and the sludge is kept in suspension during the aeration process to ensure the degradation activity of the microorganisms.

[0049] Aeration devices and stirring devices are evenly distributed in the activated sludge area. The aeration device is mainly responsible for providing oxygen to the microorganisms in the sludge to maintain an aerobic metabolic environment; the stirring device ensures that the modified Canna biochar and activated sludge are adsorbed on the plant roots and that sewage, antibiotics, Canna plant roots, modified Canna biochar and activated sludge are fully in contact, maximizing the removal efficiency of antibiotics.

[0050] This system achieves efficient removal of antibiotics by coupling the adsorption of modified Canna biochar in the rhizosphere of plants and the biodegradation of activated sludge, overcoming the problems of limited antibiotic treatment capacity and large greenhouse gas emissions of conventional activated sludge systems and plant adsorption methods. Using the sequencing batch activated sludge system of the present invention, the removal rate of antibiotics in sewage can reach 70-80%. Among them, the removal rate of sulfamethoxazole can reach more than 70%, and the removal rate of ofloxacin can reach more than 80%. After treatment, the concentration of antibiotics in sewage meets the national emission standards. The system runs stably and is easy to operate, and is suitable for large-scale sewage treatment plants.

[0051] Specifically, the modified canna biochar is prepared by the following steps:

[0052] (1) Preparation of raw Canna biochar:

[0053] The biomass raw material selected in this experiment is canna. The collected canna (roots, stems, leaves) are cut into 2-3cm small segments, washed with pure water, and placed in an oven, and dried at 85°C until completely dry. The dried canna is crushed with a grinder, and the obtained biomass is stored for later use. Take an appropriate amount of biomass and put it into a quartz boat, cover it and place it in a tube furnace. Nitrogen is introduced throughout the firing process. Biochar is prepared under anoxic conditions, and the temperature is raised to 900°C at a heating rate of 10°C / min. Continue to keep warm for 2h. After the temperature in the tube furnace cools naturally to room temperature, take out the biochar, grind it with a mortar and pass it through a 100-mesh sieve to obtain the original canna biochar, mark it as BC, and put it into a sealed bag for later use.

[0054] (2) Modification of biochar:

[0055] Preparation method of acid-modified canna biochar: Take 10g of the prepared original canna biochar and place it in a 500mL beaker, then add 300mL of concentrated HNO3 to the beaker, ultrasonicate for 30min to make it fully contact with the biochar, then stir it with a magnetic stirrer at room temperature for 2h, take it out and let the beaker stand for 2h. Filter to obtain the acid-modified canna biochar and wash it repeatedly with ultrapure water until the pH of the filtrate remains unchanged. Finally, put the collected biochar into an oven and dry it at 75℃ to constant weight to obtain acid-modified canna biochar, recorded as HBC, and put it into a sealed bag for storage.

[0056] Preparation method of alkali-modified canna biochar: use 2 mol / L KOH solution and stir with a constant temperature magnetic stirrer at 65°C. The remaining steps are the same as the preparation method of acid-modified canna biochar. Finally, alkali-modified canna biochar is obtained, recorded as KBC, and stored in a sealed bag for later use.

[0057] The biochars before and after modification were characterized by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). Figure 2 As shown in the figure, by comparing the SEM images, it can be seen that the three types of biochar are composed of irregularly shaped fragments of different sizes. Figure 2 a1~ Figure 2 a4 shows that the surface of the original Canna biochar is relatively rough, with a large number of block or spherical accumulations of different sizes, and a large pore structure can be observed; after acid-base modification, Figure 2 b1~ Figure 2 b4. Figure 2 c1~ Figure 2c4 shows that a large amount of particles loaded on the surface of HBC and KBC were removed, and the removal was more obvious after acid modification. After modification, the surface of biochar was smoother and the proportion of small pores increased significantly. This may be because the acid-base treatment changed the number and properties of functional groups on the surface of biochar and removed excess impurities by etching. SEM results show that after acid-base modification, biochar will erode the surface of the material, changing its surface morphology and pore structure. The surface of the modified biochar is smoother and the microporous structure is more obvious, indicating that the acid-base treatment significantly enhances the pore structure of biochar.

[0058] The modified Canna biochar has a higher adsorption rate and capacity than the original biochar. Specifically, it is characterized by high specific surface area and developed pore structure: Table 1 shows the structural characteristics of BC (unmodified Canna biochar), HBC and KBC. The results show that after acid-base modification, the specific surface area of ​​biochar increases, and the total pore volume and micropore volume are significantly improved, providing more adsorption sites. This feature makes the modified Canna biochar show a stronger ability to adsorb antibiotic molecules.

[0059] Table 1 Structural characteristics of BC, HBC and KBC

[0060] Biochar <![CDATA[Specific surface area (m 2 / g)]]> <![CDATA[Total pore volume (cm 3 / g)]]> <![CDATA[Micropore volume (cm 3 / g)]]> Average pore size (nm) BC 195.36 0.1122 0.0803 4.6560 HBC 1414.15 0.6803 0.5728 3.6606 KBC 1085.98 0.5378 0.4384 3.9289

[0061] Fourier transform infrared spectra of BC, HBC and KBC before and after adsorption of SMX and OFLX Figure 3 As shown, the results show that the surface of Canna biochar is rich in active functional groups such as carboxyl and hydroxyl groups, which can interact with antibiotic molecules through electrostatic effects, hydrogen bonds, etc., further improving the adsorption capacity. In addition, after alkali modification, the aromaticity is enhanced, which also increases its affinity for antibiotics.

[0062] The adsorption experiment of modified Canna biochar was carried out. The adsorption kinetic curves of SMX (sulfamethoxazole) by BC, HBC and KBC are shown in Figure 4 As shown in Figure 2, the adsorption kinetics curves of OFLX (ofloxacin) by BC, HBC and KBC are shown in Figure 2. Figure 5 As shown, it can be seen that the adsorption capacity and adsorption rate of modified canna biochar are better than those of original biochar, especially when treating complex organic pollutants (such as sulfonamides and quinolone antibiotics), the modified canna biochar shows significant adsorption advantages.

[0063] The treatment system of this embodiment operates in a batch mode, and each treatment cycle includes five stages: water intake, stirring, aeration, sedimentation, and drainage. The duration of each stage is adjusted according to the antibiotic concentration and other pollutant content in the sewage, and the duration of the entire cycle is 12 hours.

[0064] (1) Water inlet stage

[0065] First, sewage containing antibiotics enters the SBR through the water inlet. The sewage flows through the canna plant area, and the canna roots begin to initially adsorb the antibiotics. At the same time, the antibiotics in the sewage are adsorbed by the modified canna biochar. The large specific surface area and pore structure of the modified canna biochar provide a large number of adsorption sites for antibiotic molecules. This stage lasts for 30 minutes.

[0066] In this stage, plant adsorption and modified canna biochar adsorption work together to rapidly reduce the antibiotic concentration in the wastewater, so that the antibiotics no longer directly inhibit the metabolic activities of microorganisms in the sludge.

[0067] (2) Mixing stage

[0068] In this stage, the stirring blade rotates in the reactor, and the modified Canna biochar adsorbing high concentrations of antibiotics and activated sludge are adsorbed onto the plant roots together to form root activated sludge. This stage lasts for 300 minutes.

[0069] (3) Aeration and degradation stage

[0070] After the mixing is completed, the system enters the aeration stage. The aeration device begins to provide oxygen to the activated sludge area to ensure that the microorganisms maintain efficient aerobic metabolism. During this process, the microorganisms in the activated sludge can further degrade antibiotics and other organic pollutants in the sewage.

[0071] The antibiotics adsorbed by the modified canna biochar were gradually decomposed by microorganisms, which decomposed the antibiotic molecules through extracellular enzyme degradation and intracellular metabolism. This stage lasted for 300 minutes.

[0072] (4) Sedimentation stage

[0073] After aeration, the system enters the sedimentation stage. Agitation and aeration stop, and the activated sludge and other suspended solids gradually settle to the bottom of the reactor. At this point, the antibiotic concentration in the sewage has been greatly reduced, and the antibiotics adsorbed by the sludge and modified canna biochar will still be gradually degraded by microorganisms during the sedimentation process.

[0074] This stage lasts for 120 minutes. After sedimentation, the upper layer of water is relatively clear and the antibiotic content meets the national or local sewage discharge standards.

[0075] (5) Drainage stage

[0076] After sedimentation is completed, the treated sewage is discharged from the system through the drain. At this point, the removal rate of antibiotics in the sewage usually reaches 70%-90%, and it can be discharged directly or further treated (such as reuse or discharge into water bodies).

[0077] This stage lasts for 30 minutes. After drainage is completed, the system enters the next treatment cycle and continues to treat new sewage.

[0078] The processing effect analysis after the above treatment is as follows:

[0079] (1) Analysis of antibiotic removal rate

[0080] In traditional sewage treatment systems, the removal of antibiotics by simply relying on activated sludge or phytoremediation often has problems of low efficiency and unstable effects. The coupling system of modified Canna biochar and activated sludge used in the present invention greatly improves the removal rate of antibiotics. The removal rate of SMX and OFLX by the treatment system of this embodiment is shown in the following figure. Figure 6 As shown, the experimental results show:

[0081] Removal effect of sulfamethoxazole (SMX): After adding modified canna biochar, the average removal rate of SMX increased by 22.04%. Through adsorption by canna roots, adsorption by modified canna biochar, and microbial degradation in activated sludge, the concentration of SMX molecules continued to decrease in each treatment cycle, and the removal rate could reach more than 90%, ultimately achieving effective control of the SMX concentration in sewage.

[0082] Ofloxacin (OFLX) removal effect: The modified Canna biochar showed the same significant effect on the adsorption of OFLX, with a removal rate increased by 13.64%. OFLX molecules are relatively complex and difficult to degrade through conventional sludge treatment, but in this system, the modified Canna biochar provides more adsorption sites, combined with the metabolism of microorganisms, so that the removal rate of OFLX can also reach 70-80%.

[0083] (2) Reduction of greenhouse gas emissions

[0084] In the presence of antibiotics, traditional sewage treatment systems are prone to enter anaerobic conditions due to the inhibition of microbial metabolism, leading to the generation of greenhouse gases (such as methane and nitrous oxide). Through the synergistic effect of canna plants, modified canna biochar and activated sludge, the present invention significantly reduces greenhouse gas emissions. Experimental data show:

[0085] Reduction of methane emissions: Compared with traditional sequencing batch reactors, this system can reduce methane emissions by 181.87 mg per cubic meter of sewage. This is due to the rapid adsorption of antibiotics by modified canna biochar during the reaction process, which avoids the toxic inhibition of antibiotics on microorganisms and enables the system to operate under aerobic conditions.

[0086] Reduction of nitrous oxide (N2O) emissions: Aerobic metabolism of microorganisms in the system is enhanced, and the amount of nitrous oxide generated is relatively reduced. In the experiment, 15.09 mg of nitrous oxide emissions can be reduced per cubic meter of sewage. This further shows that the present invention not only improves the pollutant removal efficiency by maintaining an aerobic environment, but also reduces the carbon footprint in the sewage treatment process.

[0087] The system of this embodiment has the following advantages:

[0088] (1) High antibiotic removal efficiency: The combination of the strong adsorption of modified canna biochar and the microbial degradation of activated sludge significantly improved the system's ability to remove antibiotics.

[0089] (2) Green and environmentally friendly: Canna plants and modified Canna biochar are both natural materials, green and environmentally friendly, and do not produce secondary pollution.

[0090] (3) Low operating cost: The preparation cost of modified canna biochar is low, and the system operating cost is low, which is suitable for large-scale promotion and application.

[0091] (4) Easy to operate and highly adaptable: The batch operation mode is flexible and suitable for sewage treatment needs of different scales.

[0092] The system performs well in treating municipal sewage, livestock wastewater and agricultural wastewater, and has broad application prospects and economic benefits.

[0093] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the protection scope of the present invention.

Claims

1. A treatment system for synergistically enhancing antibiotic removal using plants and modified canna biochar, characterized in that: The method comprises a sequencing batch reactor, wherein the sequencing batch reactor is provided with a water inlet, a drain outlet, an aeration mechanism and a stirring mechanism. The bottom of the sequencing batch reactor is provided with an activated sludge coupled modified canna biochar zone, the upper part of the sequencing batch reactor is provided with a canna plant zone, and the canna plant zone is planted with canna; the water inlet is located at the lower part of the sequencing batch reactor, the drain outlet is located at the upper part of the sequencing batch reactor, and the aeration mechanism and the stirring mechanism are located in the activated sludge coupled modified canna biochar zone; The modified canna biochar is obtained by subjecting canna residue to high-temperature pyrolysis and then treating it with a strong acid or strong alkali solution.

2. The treatment system for synergistically enhancing antibiotic removal using plant and modified canna biochar according to claim 1, characterized in that: The modified Canna biochar is prepared by the following steps: The collected canna is cut into segments, washed, dried, crushed, and placed in a tubular furnace, heated to 850-900°C in an oxygen-deficient state, kept warm for more than 1 hour, and ground after cooling to obtain canna biochar; Concentrated nitric acid is added to the canna biochar, and the mixture is stirred for reaction for 2 hours, followed by filtering, washing, and drying to obtain modified canna biochar; or a KOH solution is added to the canna biochar, and the mixture is stirred for reaction at 60° C. to 80° C. for 2 hours, followed by filtering, washing, and drying to obtain modified canna biochar.

3. The treatment system for synergistically enhancing antibiotic removal using plant and modified canna biochar according to claim 2, characterized in that: Nitrogen is introduced into the tubular furnace, and the heating rate is 5-15°C / min.

4. The treatment system for synergistically enhancing antibiotic removal using plant and modified canna biochar according to claim 1, characterized in that: The concentration of the KOH solution is not less than 2 mol / L.

5. The treatment system for synergistically enhancing antibiotic removal using plant and modified canna biochar according to claim 1, characterized in that: The area of ​​the canna plant zone is 20%-40% of the cross section of the sequencing batch reactor.

6. The treatment system for synergistically enhancing antibiotic removal using plant and modified canna biochar according to claim 1, characterized in that: The activated sludge coupled modified canna biochar zone uses activated sludge and modified canna biochar mixed in a mass ratio of 1:

10.

7. A sewage treatment method, characterized in that: The treatment is carried out using the treatment system for synergistically enhancing antibiotic removal using plants and modified canna biochar as described in any one of claims 1 to 6.

8. The sewage treatment method according to claim 7, characterized in that: The steps include: Step S1, the sewage containing antibiotics enters the sequencing batch reactor through the water inlet; Step S2, starting the stirring mechanism to stir for at least 250 minutes; Step S3, stopping stirring and starting the aeration mechanism for aeration for at least 250 minutes; Step S4, stopping aeration and allowing the mixture to settle for at least 100 minutes; Step S5, after the upper layer of water after sedimentation becomes clear, draining the water through the drain outlet; Repeat steps S1 to S5 to perform the next processing cycle.

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